The present invention relates to a control apparatus for automatically stopping and restarting the engine of a vehicle having an air conditioner.
In case of a conventional vehicle driven by an engine, air-conditioning, which employs the cold air generated by an engine-driven compressor and the recycled heat of engine cooling water, has been generally provided for the cabin of a vehicle. Recently, a vehicle of idle stop, whose engine is stopped while the vehicle is not in motion, has been developed in order to reduce consumption of fuel. Also in a hybrid vehicle, which is driven by both an engine and a motor, the engine is controlled to stop while the vehicle is not in motion. When such vehicles as a vehicle of idle stop and a hybrid vehicle come to a stop while an air conditioner is in operation, a compressor for air conditioner is not able to continue operation as a result of stopping of an engine. It will consequently make the passengers uncomfortable due to temperature rise in a cabin if it is hot outside or the sun is shining brightly. On the other hand, if it is cold outside, the inconvenience of getting fogged with breathing of the passengers will occur.
Control methods, which inhibit stopping of an engine or drive a compressor by a motor while a vehicle is not in motion depending on the conditions of the outside air temperature and the like, have been developed and reported in such documents as Japanese Published Patent Applications 2000-179734 and 2001-88541.
However, the air conditioning of a conventional vehicle has not been performed so successfully that the cabin can be controlled comfortably in parallel with saving fuel by stopping an engine.
The present invention provides a control apparatus for automatically stopping and restarting the engine of a vehicle, which enables saving fuel by stopping the engine as much as possible as well as keeping a cabin comfortable.
An object of the present invention is to provide a control apparatus for automatically stopping and restarting an engine of a vehicle, which is equipped with the engine, a motor, a compressor driven by the engine and motor, an air conditioner employing a refrigerating cycle driven by the compressor and a motor control unit that controls the motor so as to drive the compressor at least while the engine is stopped. The apparatus includes a first section for making a judgment on stopping the engine and a second section for making a judgment on restarting the engine. The apparatus has features that the apparatus provides the air conditioner with a plurality of operational modes selected by a user, and when the vehicle is not in motion with selection of a first mode, the first section permits the engine to stop if a first power which the motor can supply is greater than a second power of the compressor required by the air conditioner, and the second section permits the engine to restart if the second power exceeds the first power.
The control apparatus described above permits the engine to stop if the conditions are met. Specifically, when the vehicle is not in motion, the engine is permitted to stop if the available power supplied by the motor is greater than that of compressor required by the air conditioner depending on the cabin temperature and outside air temperature. The permission of stopping the engine is given not only when the vehicle is not in motion and the engine is in operation but when the vehicle is being decelerated. In this case, the permission of stopping the engine is executed when the vehicle has come to a stop.
On the other hand, if the power of compressor required by the air conditioner exceeds that supplied by the motor, the engine is restarted, so that the engine can assist the operation of air conditioner.
In this way, the present invention enables driving of a compressor so as to keep the cabin of a vehicle comfortable while the vehicle is not in motion as well as saving of fuel by stopping an engine as much as possible.
In this connection, it is possible to select two types of approach. One is an approach of one compressor which can be driven by an engine and a motor. The other is an approach of two separate compressors driven by the engine and motor, respectively. If the latter approach is adopted, the coolant may be circulated through a shared refrigerating cycle, by uniting the outlets of respective compressors. Alternatively, it may also be possible for the compressors to have respective refrigerating cycles.
It is not limited to power, by which a comparison is made for judging a permission of stopping an engine. It may be possible to select integration of power with regard to time for a parameter
Another object of the present invention is to provide a control apparatus, which has a feature that the second section permits an engine to restart if the remaining capacity of a battery that supplies electricity to a motor falls below a predetermined value.
The apparatus described above is able to restart the engine when the remaining capacity of battery falls below the predetermined value, while a compressor is being driven by the motor while the engine is stopped. In this way, the apparatus allows not only keeping a cabin comfortable by continuing the operation of compressor while the vehicle is not in motion but also maintaining the required remaining capacity of battery.
Still another object of the present invention is to provide a control apparatus, which has a feature that when a vehicle is not in motion with selection of a second mode, the first section permits an engine to stop regardless of the second power of compressor required by an air conditioner.
Yet another object of the present invention is to provide a control apparatus, which has a feature that while an engine is stopped, a motor control unit drives a compressor within the first power that a motor can supply regardless of the second power of compressor required by an air conditioner.
The apparatus described above allows a case, where the compressor is continuously driven by the motor within the available power supplied by the motor and the engine is permitted to stop regardless of the power of compressor required by the air conditioner while the vehicle is not in motion if the second mode is selected by a user. In this way, the apparatus can not only keep the cabin of vehicle comfortable but also save fuel by stopping the engine as much as possible while the vehicle is not in motion if a user selects the second mode.